Many thermoplastic polymers per se require stabilization against discoloration when exposed to elevated temperatures. Certain materials have been found that are suitable for stabilizing a thermoplastic polymer against discoloration due to elevated temperatures. Particularly useful are certain phosphites as disclosed in U.S. Pat. No. 3,305,520 for stabilizing polycarbonates, which patent discloses solely triaryl or trialkyl phosphites as such stabilizers. Canadian Pat. No. 727,700 discloses employing trialkyl or triaryl phosphites in combination with tetraaryl tin compounds to stabilize polycarbonates. It has now been discovered that particular hydrogen phosphites are excellent in stabilizing polycarbonate resins against discoloration due to exposure at elevated temperatures.
Therefore, it is an object of this invention to provide a heat and color stable unpigmented aromatic polycarbonate resin.
Another object of this invention is to provide a heat and color stable unpigmented aromatic polycarbonate resin composition containing in admixture therewith particular hydrogen phosphites.
Yet another object of this invention is to provide a heat and color stable unpigmented aromatic polycarbonate resin composition having in admixture a polycarbonate, minor amounts of a phosphite and an epoxy.
These and other objects of this invention will become apparent from the following detailed description thereof.